log: Fix printing of signature error request headers. (#4444)

The following commit f44f2e341c
fix was incomplete and we still had presigned URLs printing
in query strings in wrong fashion.

This PR fixes this properly. Avoid double encoding
percent encoded strings such as

`s3%!!(MISSING)A(MISSING)`

Print properly as json encoded.

`s3%3AObjectCreated%3A%2A`

cmd/utils.go

@@ -17,6 +17,7 @@
 package cmd
 
 import (
+	"bytes"
 	"encoding/base64"
 	"encoding/json"
 	"encoding/xml"
@@ -163,20 +164,25 @@ var globalProfiler interface {
 func dumpRequest(r *http.Request) string {
 	header := cloneHeader(r.Header)
 	header.Set("Host", r.Host)
+	// Replace all '%' to '%%' so that printer format parser
+	// to ignore URL encoded values.
+	rawURI := strings.Replace(r.RequestURI, "%", "%%", -1)
 	req := struct {
-		Method string      `json:"method"`
-		Path   string      `json:"path"`
-		Query  string      `json:"query"`
-		Header http.Header `json:"header"`
-	}{r.Method, getURLEncodedName(r.URL.Path), r.URL.RawQuery, header}
-	jsonBytes, err := json.Marshal(&req)
-	if err != nil {
+		Method     string      `json:"method"`
+		RequestURI string      `json:"reqURI"`
+		Header     http.Header `json:"header"`
+	}{r.Method, rawURI, header}
+
+	var buffer bytes.Buffer
+	enc := json.NewEncoder(&buffer)
+	enc.SetEscapeHTML(false)
+	if err := enc.Encode(&req); err != nil {
 		// Upon error just return Go-syntax representation of the value
 		return fmt.Sprintf("%#v", req)
 	}
-	// Replace all '%' to '%%' so that printer format parser
-	// to ignore URL encoded values.
-	return strings.Replace(string(jsonBytes), "%", "%%", -1)
+
+	// Formatted string.
+	return strings.TrimSpace(string(buffer.Bytes()))
 }
 
 // isFile - returns whether given path is a file or not.